Sensor joined to a glass pane with a silicon gel

ABSTRACT

A gel is used as the joining agent to mount a rain sensor to a windscreen of an automobile. The gel used does not harden even in the long term, and air pockets which form inside the gel or on the boundary surfaces with the glass pane or the sensor migrate into the area around the sensor. The rain sensor is attached to a glass pane without special elastic intermediate elements, using the elasticity of the joining agent for tolerance compensation.

BACKGROUND OF THE INVENTION

WO 96/21568 describes a method for joining a sensor to a glass pane withthe aid of a transparent adhesive tape. In this case, a so-calledacrylic foam may, for example, be utilized as the join medium. Thismaterial rigidly adheres to the glass pane and is very difficult toremove. The mounting of a sensor on a glass pane requires a vacuum and,under certain circumstances, the prior heating of the glass pane inorder to obtain a joint without air bubbles. If the sensor emits orreceives radiation, it is frequently desired to incorporate aninfrared-permeable daylight filter (black appearance). However, acorresponding black coloring of the acrylic foam is not possible.Long-term temperature tests at 100 degrees resulted in yellowing andhardening of the acrylic foam. These aging phenomena have negativeeffects on the function and the mechanical retention of the sensor.Consequently, the invention is based on a joining medium silicone gel.

The invention aims to disclose a non-hardening, transparent joiningmedium that can be colored such that it is permeable to infraredradiation and ensures a permanent and superior joining of a sensor tothe respective body.

SUMMARY OF THE INVENTION

The invention, in principle, consists of utilizing a gel that remainssoft. Such a gel is, for example, available on the market under thedesignation SilGel 612 from Wacker. One preferably utilizes a colorlesssilicone gel that has a viscosity of approximately 800-1200 mm2/s at 23degrees C. and a density of approximately 0.96 g/cm3. The index ofreaction n025 may have a value of approximately 1.4026 at 25 degrees C.The aforementioned silicone gel is frequently referred to as RTV-2caoutchouc silicone and is available on the market under the trade nameSemicosil 912 from Wacker Chemie GmbH.

The main advantages of this gel can be seen in the fact that it cannotharden, and that it remains a soft, gelatine-like vulcanized materialeven after a prolonged period of time and after being subjected to heatand insolation for prolonged periods of time. Another important aspectregarding the gel is that it cannot permanently enclose air particles.These air particles are removed from the gel due to their naturalmovement after a certain period of time. The gel also prevents stressbetween the housing of the sensor and the glass pane to which the sensoris joined.

One particular advantage of the gel used can be seen in the fact that itcan be colored with a dye that is permeable to infrared measuringradiation, with said dye largely acting as a filter for other (light)radiation such that the measuring accuracy of a measuring device (e.g.,a rain sensor) that operates with infrared radiation can be increased.

It appears possible to directly join the transmitter and/or receiver(sensor) to the glass pane by means of admixtures to the silicone gel.The present invention also discloses a new method for mounting thesensor on a body, in particular, a windshield, which utilizes thepreviously described joining medium. In this case, the objectiveconsists of simply pressing the sensor onto the windshield by means of aprestress by utilizing the joining gel. In this respect, it was proposedto elastically join the sensor to the glass pane by means of the gelwith the aid of a spring element that is supported on the glass pane,e.g., a spring element that is arranged in the bracket of a rearviewmirror which contacts the glass pane. According to the invention, asensor is particularly suitable for this mounting method. Consequently,the invention, in principle, consists of utilizing a gel of thepreviously described type as the joining medium for this mountingmethod, with the transmitter and/or receiver being combined in the formof a transceiver that operates as a rain sensor. The radiation emittedand received by the rain sensor preferably consists of infrared light,with the joining medium being colored with a dye that is permeable toinfrared light, in particular, a black dye. Due to this measure, therain sensor that is usually provided with a dark housing has an entirelyblack appearance such that the joining medium which is visible throughthe glass pane cannot be optically differentiated from the rest of thesensor housing.

In order to ensure that the detectors and radiation elements arrangedwithin the sensor and the receiver have exactly the prescribed distancefrom the glass plane surface, the invention proposes the additionaldevelopment defined by the projections maintaining an exact distancebetween the transmitter and/or receiver and the glass pane. In addition,the resulting channels ensure that excess gel is able to escape.Consequently, the gel situated between the sensor surface and the glasspane not only has a predetermined thickness, but the desired density canalso be obtained largely independent of the quantity introduced duringthe mounting process. In this respect, it is possible to apply aslightly larger quantity of the gel than required onto the surface ofthe sensor which faces the windshield. When the sensor or the sensorhousing is subsequently pressed onto the glass pane with its frontcircumferential edge, the excess gel is able to laterally escape throughprojections such that the gel is always arranged between the sensor andthe glass pane with the same stress and the same density. In order topreserve the density and the stress in the joining medium (gel), theinvention proposes the additional development in which as mentionedpreviously, it was proposed to generate prestress by means of additionalsprings that are supported on the glass pane. This particular variationcan be simplified by utilizing an additional development of theinvention which is defined by the combination of characteristicsproposes that a holder which acts upon the sensor in a largely rigidfashion is mounted on the glass pane. In this case, the elastic effectis not achieved by means of an additional spring, but rather by thespring effect of the joining medium (gel). Due to this measure, alargely uncomplicated construction for the holder is achieved. In thuscase, the wall of the holder is initially connected to the glass paneduring the mounting process, whereafter the sensor with its housing andthe applied joining medium is inserted into the wall of the holder.Subsequently, the cover is connected to the wall of the holder byexerting a force in the direction of the glass pane. However, otherconstructions would also be conceivable. For example, the sensor housingcan be directly locked in the wall of the holder, or the holder with theinserted sensor (and joining medium) can be mounted (bonded) to theglass pane by exerting a pressing force.

The shape of the wall of the holder is adapted to the outer contour ofthe sensor. This wall has a particularly simple design if the sensor hasan essentially circular shape, i.e., the wall has an annular appearance.

The function of the holder does not necessarily have to consist ofproviding a support for the sensor relative to the glass pane. Theholder may also accommodate electric connections, e.g., in the form of amultiple plug. These electric connections make it possible to connectthe sensor to the corresponding electric units during the mountingprocess. The power supply may also be realized via the electricconnections of the holder.

The holder may, in principle, be simply bonded to the glass pane bymeans of adhesive agents. However, it would also be conceivable to lockthe holder on the glass pane by means of locking elements that are castinto the glass pane. A particularly simple arrangement for the holder isproposed in a combination of characteristics in which the holder isshaped out of the glass pane material or cast into the glass pane. Forexample, a holder that consists of metal or plastic is cast into theglass pane during its manufacture. However, the glass pane material canalso be directly shaped into a holder. Accordingly, connecting lineswhich lead to the holder are not bonded onto the glass pane in thiscase, but directly cast into the glass pane.

If the quantity of the joining medium situated between the sensor andthe glass pane is precisely metered, the sensor can be arranged at aprescribed distance from the glass pane and the joining medium can beprovided with the desired density between the sensor and the glass pane,e.g., if the holder and the sensor are subject to strict tolerances.However, in order to allow an additional tolerance, the inventionproposes an additional development in which the projections do notnecessarily have to contact the glass pane in order to exactly maintainthe corresponding distance. It suffices if the projections formchannels, through which the excess joining medium can be laterallypressed out due to a predetermined force, i.e., the gel subsequently hasa predetermined thickness. The width of the channels consequentlyinfluences the stress to which the gel is subjected in the joined state.

The snap-in connection between the holder and the sensor in accordancewith the invention can also be utilized for separating this connectionif a permissible lateral force is exceeded. In this case, the sensor isfreely movable relative to the glass pane such that the risk of injuriesdue to a projecting sensor is eliminated during an accident

BRIEF DESCRIPTION OF THE DRAWING

One embodiment of the invention is described below with reference to thefigures which show:

FIG. 1 is an exploded view of the holder with the sensor;

FIG. 2 is a view of the sensor in its mounting position on the glasspane (without a holding ring);

FIG. 3 is a top view of the sensor according to FIG. 2;

FIG. 4 is a front view of the sensor according to FIG. 2;

FIG. 5 is a section through the sensor with a holder cover along theline A—A in FIG. 2;

FIG. 6 is a sectioned side view of the sensor according to FIG. 2;

FIG. 7 is an enlarged detail of FIG. 6;

FIG. 8 is a top view of the sensor with a holder cover and a holdingring which corresponds to the top view according to FIG. 3, however,with a modified cover mounting;

FIG. 9 is a schematic representation of the interlocking between theholder cover and the holding ring according to FIG. 8;

FIG. 10 is a side view of the interlocking according to FIG. 9, and

FIGS. 11 and 12 are views of a sensor with a modified cover whichcorrespond to the view shown in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a sensor 3 that can be inserted into a sensor housing 2.The sensor housing 2 contains a plug, with plug sockets 5 beingcontacted with a series of plugs 6 when inserting the sensor 3 into thehousing 2. A holder that consists of a holding ring 1 (frequentlyreferred to as the wall of the holder above) and a cover 4 accommodatesthe sensor housing 2 with the inserted sensor 3. The cover 4 containslocking tabs 7 that engage into corresponding recesses 8 when mountingthe sensor 2, 3 in the holder 1, 4. The holder is connected to anot-shown glass pane by means of an adhesive connection.

FIG. 2 shows an enlarged representation of the sensor housing 2, ontowhich the holder cover 4 with its locking tabs 7 is attached. The ring,or wall 1, of the holder was omitted in order to illustrate the layer ofthe joining medium 10 arranged on the windshield 11 of a motor vehicle.

FIG. 3 shows the sensor 3 with the holder cover 4 in the form of a topview, with only the plug 9 of the sensor housing 2 being visible in thiscase.

FIG. 4 shows the sensor with the cover in the form of a view that isdirected onto the plug 9.

FIG. 5 shows a section along the line A—A in FIG. 2, with the sensor 3situated within its housing 2 also being recognizable in the form of asection. Outside of the circumference of the housing 2, the holding ringis shown in its not yet installed position. In the installed position,the holding ring is bonded to the glass pane by means of a not-shownadhesive layer. FIG. 2 also shows the projections 12 which ensure apredetermined thickness of the layer of the joining medium 10.

In FIG. 5 and FIG. 10, the holding ring 1 is shown with an inclinedadhesive surface 13 relative to the glass pane surface. An essentiallyannular adhesive layer 14, the thickness of which decreases radiallyinward in the form of a wedge, is situated between the adhesive surface13 and the glass pane 11. The holding ring 1 contains a sealing strip 15on its radially inner side which is intended to prevent the adhesive 14from flowing toward the sensor housing 2 such that the housing can beeasily removed from the holding ring 1. The adhesive surface 13 does notnecessarily have to be inclined relative to the glass pane. In numerousinstances, it is advantageous to maintain this adhesive surfaceessentially parallel to the glass pane 11 such that the adhesive layer14 has the shape of an annular disk. This reduces the quantity ofadhesive mass used and, if so required, increases the adhesive force.

FIGS. 1-7 show a first method for mounting the sensor 3 in the holder 1,4. In this case, projections 17 which protrude radially outward on thelocking tabs 7 engage into corresponding recesses 8 (see FIG. 1) in theholding ring 1 of the holder.

FIGS. 8-10 show a second mounting method, in which tangentiallyextending projections 18 engage into corresponding recesses 19 in theholding ring 1 of the holder. In this case, two projections 18 that canbe subjected to excursions in opposite directions are respectivelyprovided on the tabs 7. Another option which is realized similar to thatshown in FIGS. 1-7 is illustrated in FIGS. 11 and 12. In this case,projections 17 that point radially outward are provided. The novelty ofthis option can be seen in the fact that the ends 20 of the locking tabs7 on the side of the cover positively engage on the outer edge of thesensor 3. In this case, a circumferential projection 22 may, forexample, engage into a circumferential recess 23 in the housing 2 so asto center the cover 4 and fix said cover 4 in the direction that extendsperpendicular to the glass pane 11 such that the locking force of theprojections 17 can be defined more precisely.

FIGS. 3 and 8 indicate that the circumferential recess 23 and thecircumferential projection 22 may essentially extend circularly, withthe cover only being supported on the housing at three points in thevariation according to FIG. 12.

What is claimed is:
 1. A device for mounting a rain sensor on a bodycomprising: a silicone gel permeable to infrared light joining the rainsensor to the body; the rain sensor rigidly embedded in a sensorhousing; an edge of the sensor housing resting on the body having localprojections; and a holder supporting the sensor housing on the body, theholder including: a wall protruding from the body, the wallaccommodating a portion of the sensor housing; and a cover enclosing thesensor within the sensor housing, the cover having locking tabsconnectable to respective recesses in the wall and having at least oneof a radially-extending projection and a radially-extending recess suchthat, in a closed position, the at least one of the radially-extendingprojection and the radially-extending recess of the cover respectivelyengages one of a radially-extending recess and a radially-extendingprojection of the housing.
 2. The device according to claim 1, whereinthe projections form intermediate spaces through which excess siliconegel can escape.
 3. The device according to claim 1 wherein: dimensionsof the holder, the sensor and the silicone gel are chosen such that thesensor is pressed against the elastically acting silicone gel in itsmounted condition.
 4. The device according to claim 3, wherein theinterlocked connection is provided with at least one predeterminedbreaking point that separates the connection under a defined openingforce.
 5. The device according to claim 1 wherein the housing containselectric connections that serve for one of receiving signals from thesensor and for supplying the sensor with power.
 6. The device accordingto claim 1 further comprising: one of the holder and the sensor housingcontaining lateral openings within the region of the silicone gel, withthe lateral openings allowing excess silicone gel to escape through theopenings.
 7. The device according to claim 6, wherein the openings areformed by projections that extend essentially perpendicular to thesurface of the body and are supported on the surface.
 8. The deviceaccording to claim 1 wherein a portion of the wall is integrally moldedwith the body.
 9. The device according to claim 1 wherein the at leastone of the radially-extending projection and the radially-extendingrecess of the cover is one element extending about the outer peripheraledge of the cover.
 10. A device for mounting a rain sensor to awindshield of a vehicle, comprising: a silicone gel joining a portion ofa facing surface of the rain sensor to the windshield; a sensor housingsurrounding at least an outer peripheral edge of the rain sensor;projections extending from a surface of the sensor housing facing thewindshield, the projections in contact with the windshield; and a holderengaged about an outer peripheral edge of the sensor housing, the holderincluding: a sealing strip extending along an inside edge of the holder,the sealing strip in contact with the windshield and spaced from theouter peripheral edge of the sensor housing; an adhesive surfaceextending away from the sealing strip, the adhesive surface opposed toand spaced from the windshield; and an inner surface extending from thesealing strip and away from the windshield to contact the sensorhousing.
 11. The device according to claim 10 wherein the adhesivesurface is inclined in a direction away from the sensor housing.
 12. Thedevice according to claim 10 wherein the holder further comprises acover with locking tabs engageable with at least one recess spaced abouta surface of the holder opposite the adhesive surface.
 13. The deviceaccording to claim 10, further comprising: an electrical connectorextending from the outer peripheral edge of the sensor housing.
 14. Thedevice according to claim 10 wherein the silicone gel is dyed to a colorpermeable to infrared light.
 15. The device according to claim 14wherein the silicone gel is dyed black.
 16. A device for mounting a rainsensor to a windshield of a vehicle, comprising: a silicone gel joininga portion of a facing surface of the rain sensor to the windshield; ahousing extending between the windshield and the rain sensor for aremainder of the facing surface of the rain sensor and extending from asurface of the windshield to enclose an outside peripheral edge of thesensor; and projections extending from a surface of the housing facingthe windshield, the projections in contact with the windshield.
 17. Thedevice according to claim 16 wherein the projections are spaced to allowexcess silicone gel to escape.
 18. The device according to claim 16,further comprising: a holder supporting the housing on the windshield,the holder including a wall protruding from the windshield andaccommodating a portion of the housing, wherein at least a portion ofthe holder is integrally molded with the windshield.
 19. A device formounting a rain sensor that operates with radiation on a body with therain sensor being joined to the body with silicone gel comprising:silicone gel being colored with a dye that is permeable to infraredlight; the rain sensor being rigidly embedded in a sensor housing; anedge of the sensor housing which rests on the body being provided withlocal projections; and a holder mounted on the body, with the holderengaging on the sensor by one of directly and by an essentially rigidintermediate element and the holder indirectly pressing the sensoragainst the body via the silicone gel, wherein the holder is realizedintegrally with the body.
 20. A device for mounting a rain sensor thatoperates with radiation on a body with the rain sensor being joined tothe body with silicone gel comprising: silicone gel being colored with adye that is permeable to infrared light; the rain sensor being rigidlyembedded in a sensor housing; an edge of the sensor housing which restson the body being provided with local projections; and a holder mountedon the body, with the holder engaging on the sensor by one of directlyand by an essentially rigid intermediate element and the holderindirectly pressing the sensor against the body via the silicone gel,wherein electric supply lines leading to the holder extend within thebody.